Chris was waiting for me by my car when I came out of school after a distracted day’s teaching – I had been unable to stop thinking about Elsa Brown. An image of her stuck there, dying on the carpet played continuously across my mind.

It wasn’t helped by the detail one of the police officers had provided. She’d died on the way to the hospital. That meant she’d been lying there on her own as her life ebbed away.

‘You’ve been thinking about this all day, haven’t you?’ Chris said.

I nodded.

He put a hand on my shoulder. ‘You can’t go there, John.’ He offered me a small smile. ‘It was an accident. And if there is anything nefarious going on, it’s past actions coming home to roost.’

‘How can you be so callous?’ I asked.

‘Pragmatic I’d call it.’

‘But…’

‘But nothing, John. Let’s not forget we’re dealing here with people who were trafficking children. As far as I’m concerned she got what was coming to her…’ he paused ‘…if it wasn’t an accident.’

My boss, Alex White, appeared, with his briefcase under his arm, pointing a key fob at a large silver Ford.

‘John,’ he acknowledged me with a nod. When he looked at Chris his expression soured. ‘I hear the police interviewed you today?’ His mouth was a tight line of reprimand.

‘I do some charity work in the evening.’ I had no idea where the lie came from but I had no intention of telling White the truth. ‘And one of the old ladies I visit now and again died in the early hours of this morning.’

‘That’s terrible,’ he said, but he appeared mollified at the idea that one of his staff was doing some form of community work. ‘Well, be sure to have some rest tonight so you’re back in tip-top form for your pupils in the morning.’

‘Will do,’ I said.

Ten minutes later Chris and I were facing each other at a table in a nearby coffee shop. The shop window was covered in a net curtain, the Anaglypta walls were decorated with postcards, and there was a giant aluminium urn instead of a proper coffee machine. The baristas of the West End hadn’t quite reached this neighbourhood.

‘What are you thinking?’ I asked.

‘I can understand if you’re feeling a bit wobbly about all of this, but the most likely explanation is that Mrs Brown actually did trip over her dog and hit her head on the marble hearth. We both saw the mutt was always under her feet.’

‘And if it wasn’t an accident?’ I said.

‘There’s nothing about this that suggests it wasn’t, John.’

‘Yeah, but what if? What if someone killed Elsa Brown to keep her silent, and we’ve kicked a hornet’s nest? Are we in danger?’ I had an image of me going home that evening and crawling across the living room floor to close the curtains in case anyone could see in and take a shot at me.

‘Why would they come after you? You don’t know anything.’

‘Tell me to shut up,’ I said. ‘I’m being paranoid.’

‘If – and it’s a big if – we have prodded a bear, what do you think? Take a step back for a while and let it go back to sleep?’

‘I just…’ Exasperated I threw myself back in my chair. ‘I can’t help thinking Elsa Brown would still be alive if we hadn’t gone to visit her. And the logical conclusion from that is someone is going to extraordinary lengths to keep their secrets hidden.’ I crossed my arms, feeling small and regretting that I’d ever found that photograph in my parents’ loft. ‘If they’re crazy enough to kill a defenceless old woman…’